/*
 * ------------------------------------------------------------------------
 *  Copyright by KNIME AG, Zurich, Switzerland
 *  Website: http://www.knime.com; Email: contact@knime.com
 *
 *  This program is free software; you can redistribute it and/or modify
 *  it under the terms of the GNU General Public License, Version 3, as
 *  published by the Free Software Foundation.
 *
 *  This program is distributed in the hope that it will be useful, but
 *  WITHOUT ANY WARRANTY; without even the implied warranty of
 *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
 *  GNU General Public License for more details.
 *
 *  You should have received a copy of the GNU General Public License
 *  along with this program; if not, see <http://www.gnu.org/licenses>.
 *
 *  Additional permission under GNU GPL version 3 section 7:
 *
 *  KNIME interoperates with ECLIPSE solely via ECLIPSE's plug-in APIs.
 *  Hence, KNIME and ECLIPSE are both independent programs and are not
 *  derived from each other. Should, however, the interpretation of the
 *  GNU GPL Version 3 ("License") under any applicable laws result in
 *  KNIME and ECLIPSE being a combined program, KNIME AG herewith grants
 *  you the additional permission to use and propagate KNIME together with
 *  ECLIPSE with only the license terms in place for ECLIPSE applying to
 *  ECLIPSE and the GNU GPL Version 3 applying for KNIME, provided the
 *  license terms of ECLIPSE themselves allow for the respective use and
 *  propagation of ECLIPSE together with KNIME.
 *
 *  Additional permission relating to nodes for KNIME that extend the Node
 *  Extension (and in particular that are based on subclasses of NodeModel,
 *  NodeDialog, and NodeView) and that only interoperate with KNIME through
 *  standard APIs ("Nodes"):
 *  Nodes are deemed to be separate and independent programs and to not be
 *  covered works.  Notwithstanding anything to the contrary in the
 *  License, the License does not apply to Nodes, you are not required to
 *  license Nodes under the License, and you are granted a license to
 *  prepare and propagate Nodes, in each case even if such Nodes are
 *  propagated with or for interoperation with KNIME.  The owner of a Node
 *  may freely choose the license terms applicable to such Node, including
 *  when such Node is propagated with or for interoperation with KNIME.
 * ------------------------------------------------------------------------
 */
package org.knime.base.node.parallel.appender;

import java.util.NoSuchElementException;

import org.knime.core.data.DataRow;
import org.knime.core.data.DataTable;
import org.knime.core.data.DataTableSpec;
import org.knime.core.data.RowIterator;

/**
 * Simples helper table whose iterator just concatenates all the tables passed
 * in the constructor. <b>The implementation does not check if the row keys
 * in the passed tables are unique, so you have to assure that by yourself!</b>
 * 
 * @author Thorsten Meinl, University of Konstanz
 */
class CombinedTable implements DataTable {
    private final DataTable[] m_tables;

    /**
     * Creates a new combined table.
     * 
     * @param tables the tables to combine
     */
    public CombinedTable(final DataTable... tables) {
        if ((tables == null) || (tables.length < 1)) {
            throw new IllegalArgumentException("At least one table must be "
                    + "given");
        }
        m_tables = tables;

        for (int i = 1; i < m_tables.length; i++) {
            if (!m_tables[0].getDataTableSpec().equalStructure(
                    m_tables[i].getDataTableSpec())) {
                throw new IllegalArgumentException("The table at index " + i
                        + " has an incompatible spec");
            }
        }
    }

    /**
     * {@inheritDoc}
     */
    public DataTableSpec getDataTableSpec() {
        return m_tables[0].getDataTableSpec();
    }

    /**
     * {@inheritDoc}
     */
    public RowIterator iterator() {
        return new RowIterator() {            
            private RowIterator m_it = m_tables[0].iterator();
            private int m_nextTableIndex = 1;
            
            @Override
            public boolean hasNext() {
                if (m_it.hasNext()) {
                    return true;
                }
                
                if (m_nextTableIndex >= m_tables.length) {
                    return false;
                }
                
                m_it = m_tables[m_nextTableIndex++].iterator();
                return m_it.hasNext();
            }

            @Override
            public DataRow next() {
                if (hasNext()) {
                    return m_it.next();
                } else {
                    throw new NoSuchElementException("No more rows");
                }
            }            
        };
    }
}
